1. Field of Technology
The present invention relates to an organic light emitting diode (OLED) display device, and more particularly, to a method and apparatus for controlling current of an OLED display device, which is able to accurately estimate the amount of current according to an input image and control current to converge upon a target current.
2. Discussion of the Related Art
An OLED display device is a self-emissive device for emitting light using an organic light emitting layer due to re-combination between electrons and holes and is expected to be a next-generation display device due to high luminance, low driving voltage and slimness of the OLED display device.
Each of a plurality of pixels (subpixels) configuring an OLED display device includes an OLED element including an organic light emitting layer between an anode and a cathode and a pixel circuit for independently driving the OLED element. The pixel circuit includes at least a switching transistor, a storage capacitor and a driving transistor. The switching transistor charges the storage capacitor with a voltage corresponding to a data signal in response to a scan pulse and the driving transistor controls current supplied to the OLED element according to the voltage charged in the storage capacitor so as to adjust the amount of light emitted by the OLED element. The amount of light emitted by the OLED element is proportional to current supplied from the driving transistor.
In order to reduce power consumption, a conventional OLED display device generally uses a method of controlling current by controlling a peak luminance, that is, a method of controlling current of a display panel by controlling a peak luminance (maximum white luminance) according to an input image so as to adjust a gamma voltage.
In the conventional OLED display device, a peak luminance is controlled by estimating the amount of current on the assumption that the amount of current is linearly proportional to luminance. However, actually, in the OLED display device, since the amount of current is non-linearly proportional to luminance, it is difficult to accurately estimate the amount of current according to the input image. Therefore, since a difference between an estimated current value and a target current occurs, it is difficult to accurately control current.